Oblique shock

About: Oblique shock is a research topic. Over the lifetime, 6551 publications have been published within this topic receiving 119823 citations.

Flow Nonuniformity in Shock Tubes Operating at Maximum Test Times

Abstract: Shock tube flow nonuniformity is investigated in the limit where the shock and contact surface have reached their maximum separation. Ideal gases are considered. It is found that all fluid properties increase in value between the shock and contact surface. The nonuniformity is greatest when γ (ratio of specific heats) is large and Ms (shock Mach number) is low. For γ = 53 and Ms ≥ 3, the static temperature, density, and pressure increase by about 8, 12, and 20%, respectively; the stagnation temperature increases by about 35%, and the stagnation pressure, dynamic pressure, and stagnation point heat transfer increase by about a factor of 2. These results apply to turbulent as well as laminar boundary layers. The variation of flow properties with distance behind the shock, as well as particle time of flight, is given for both wholly laminar and wholly turbulent wall boundary layers. These results are particularly important for chemical rate and heat transfer studies.

The structure of oblique subcritical bow shocks: ISEE 1 and 2 observations

Abstract: ISEE 1 and 2 spacecraft magnetic field data are used to determine the scale lengths of various elements of shock structure, as well as wavelengths and wave polarizations, in a study of structural elements which include shock ramps and precursor wave trains over a series of oblique, low Mach number terrestrial bow shocks. Dissipative processes are reflected in the damping of the precursors, and dissipative scale lengths are of 200-800 km, or several times greater than shock thicknesses. The source of dissipation in the shocks does not appear to be the wave-wave decay of the whistlers, for which no evidence is found. The interaction of the whistler itself with upstream electrons is suggested as a simple and self-consistent explanation for the observed wave train damping.

Escape of heated ions upstream of quasi-parallel shocks

Abstract: A simple theoretical criterion by which quasi-parallel and quasi-perpendicular collisionless shocks may be distinguished is proposed on the basis of an investigation of the free escape of ions from the post-shock plasma into the region upstream of a fast collisionless shock. It was determined that the accessibility of downstream ions to the upstream region depends on upstream magnetic field shock normal angle, in addition to the upstream plasma parameters, with post-shock ions escaping upstream for shock normal angles of less than 45 deg, in agreement with the observed transition between quasi-parallel and quasi-perpendicular shock structure. Upstream ion distribution functions resembling those of observed intermediate ions and beams are also calculated.

The interaction of a shock with a vortex: Shock distortion and the production of acoustic waves

Abstract: Numerical simulations of a shock interacting with a compressible vortex are presented for shocks and vortices of various relative strengths. The simulations show the effects of the vortex on the shock structure and the structure of the acoustic field generated by the shock–vortex interaction. A relatively weak vortex perturbs the transmitted shock only slightly, whereas a strong vortex leaves the transmitted shock with a structure corresponding to either a regular or Mach reflection. The acoustic wave generated by the interaction consists of two components: a ‘‘quadrupolar’’ component produced by the initial shock–vortex interaction and the complex reflected shock system. When these waves merge, they form the asymmetric structure seen in experiments.

On the passage of a shock wave through a dusty-gas layer

Abstract: The flow resulting from the passage of a shock wave through a dusty-gas layer is studied theoretically. On the basis of an idealized equilibrium-gas approximation, the criteria for the wave reflexion at the contact surface separating the pure gas from the dusty-gas layer are obtained in terms of the properties of the gas and the dusty gas. For the cases treated here, a shock wave is reflected at the first contact surface and a shock wave stronger than the incident one is transmitted into the dusty-air layer. Subsequently, a rarefaction wave is reflected at the second contact surface and the shock wave transmitted into the free air is weakened by this nonlinear interaction. The induced rarefaction wave reflects later at the first contact surface as a compression wave, which runs through the layer to overtake the transmitted shock wave in air. The final emergent shock wave from the dusty air has almost the same strength as the original shock wave entering the layer. The time-dependent transition properties through the shock waves, contact surfaces and rarefaction waves are found by solving the equations of motion numerically by a modified random-choice method with an operator-splitting technique.